How to extract ISO year in ClickHouse ® : toISOYear vs toYear

ClickHouse provides the toISOYear() function, enabling users to extract the ISO 8601 week-numbering year, which differs from the traditional calendar year by starting on the Monday of the first week containing at least four days of the new year. This function is crucial for generating accurate weekly reports and time series analytics, as it avoids the distortion caused by partial weeks at year boundaries. The function works with various date types, automatically handling timezone conversions, and returns a UInt16 integer representing the year. It is particularly useful for grouping data by complete weeks in business intelligence applications, ensuring consistent and meaningful time-based analyses. The article also discusses performance optimization strategies, such as using materialized columns and projections to enhance the efficiency of ISO year calculations in large datasets. Moreover, the text explains how to create production APIs using Tinybird's managed ClickHouse platform for real-time analytics, demonstrating the practical application of ISO year calculations in building robust and scalable data solutions.